In the horizontal directional drilling (HDD) business, many items become key to a successful completion of a project. Having worked with contractors throughout North America over the last 10 years, I have received many calls with problems ranging from site conditions to tooling. I call on my experience and that of many industry contacts to help in any way I can.
The call that came on July 2 was no exception. Bill Harrison of Southwestern Road Boring was working on a project in southwestern Arkansas and having problems with excessive wear on his tooling, not to mention the difficulties encountered trying to complete the bores in a timely manner. Harrison had about 1.5 miles of 4-in. gas line to install in very difficult site and soil conditions.
The jobsite is near the Navaculite mine in Hot Springs, Ark. This is the name of the Arkansas stone that is used in the manufacture of sharpening stones. Railhead’s Steve Mayer and I met with Harrison and his crew at the jobsite. We were asked to provide solutions to the problems presented by this project. After looking over the soil conditions, we found the stone that had been described to us, as well as some Quartzite formations mixed in.
When working with contractors, I stress the need to eliminate as many strikes against you as possible before starting the bore. This includes having the right drill, with the right crew, mixing the right mud mix and, finally, choosing the right tools for the job. By doing this along with mustering up all the patience you have, successful rock bores can become an every day story for today’s contractors.
The pilot bore had been completed before we arrived. The bore was only 200 ft long, but the tooling used was completely worn out. Harrison told us the tooling was brand new before this bore and came out looking like a pencil point. He said he felt he was “lucky” to not have any damage to the sonde, noting that he believed it too would have been destroyed had the bore been any longer.
The outside diameter of the gas line is more than 5 in. The inspector required the pipe to be virtually “scar free” when it came through the bore. Because of this requirement, our recommendation was to drill the future pilot bores with a Railhead Incredibit and the back ream should be done with an EXTReam reamer. By using an Incredibit, Southwestern Road Boring was able to create a pilot bore of more than 6 in.
The EXTReam rock reamer is built with no bearings that may fail due to pull back pressure or rotational speed. Many contractors have experienced bearing problems with small-size hole-openers because of the high pull back pressures and rotation speed required for the hole-openers to perform properly. The EXTReam reamer requires very little pull back pressure to perform. We recommend starting at 500 lbs and changing to provide optimum performance. The crew for this project was able to back ream this first bore with only 400 lbs of pull back pressure. Back ream speed was approximately 8 to 10 minutes per 10-ft rod. This resulted in a minimum of wear to the tooling and drill rods. By building a 12-in. hole to pull the product through, the inspector was very pleased with the condition of the pipe when it came out of the hole.
As is evidenced by the wear on the collar shown in the picture (see page 52), it is obvious that the conditions at this site are extremely abrasive. Harrison was glad to see the EXTReam had virtually no wear to the body. His only repair was to simply replace the teeth in the reamer. After a day that was filled with equipment problems, thunderstorms and even flight delays trying to get to the job, Harrison was still happy that they had a successful bore and solutions to the problems he originally called us with.
Dave Helgeson is director of sales and marketing at Railhead Underground Products, based in Weatherford, Texas.